Liquid galley refrigeration system for aircraft

ABSTRACT

The liquid galley refrigeration system for cooling food carts for aircraft employs an intermediate working fluid to transfer heat from one or more food carts to one or more remote chillers, allowing the carts and chillers to be advantageously distributed in the aircraft. A plurality of heat exchanges effect a cooling of the carts wherein heat from the food cart is first transferred to a first airflow; heat from the first airflow is then transferred to an intermediate working fluid that is circulated between a location immediately adjacent the food carts and a remote chiller; heat from the intermediate working fluid is subsequently transferred to the chiller working fluid; and finally, heat from the chiller working fluid is expelled. While the chiller working fluid undergoes a phase change in order to transfer heat from the intermediate working fluid to the cooling air, the intermediate working fluid remains in its liquid phase throughout its circulation. A recirculation pump circulates the intermediate working fluid through a distribution system that may link a plurality of chillers to a plurality of food carts, and the temperature of the food carts is regulated by a combination of controls.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/603,262,filed 20 Nov. 2006, now U.S. Pat. No. 7,421,849; which is a continuationof application Ser. No. 11/081,446, filed 16 Mar. 2005, now U.S. Pat.No. 7,137,264, issued 21 Nov. 2006; which is a continuation ofapplication Ser. No. 09/947,222, filed 5 Sep. 2001, now U.S. Pat. No.6,880,351, issued 19 Apr. 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to transport aircraft galley systems, and moreparticularly, to systems to cool food carts prior to service by thecabin attendants.

2. Description of Related Art

Aircraft galley systems for modern transport aircraft incorporate foodcarts which are cooled to prevent food spoilage prior to use by thecabin attendants for distribution of food to the passengers. These foodcarts have in the past been interfaced with cold air supply systems inthe galley designed to cool the interiors of the food carts. Such coolair distribution systems were generally co-located with the balance ofthe galley and interface to the food carts by means of gasketsconnecting the food carts to a plenum containing the cool air.

As space in modern aircraft has become more at a premium and moreefficient means of cooling the carts has become necessary, there hasemerged a need for alternatives to such systems. Furthermore, recent FDArulings have lowered the required temperature at which the interior ofthe food carts has to be kept in order to prevent food spoilage.Additionally, it has become more desirable to remove refrigerationequipment from the galley compartment and to find other means toproperly cool the food carts without locating the entire refrigerationsystem in the galley area. In order to be compatible with moderntransport aircraft requirements, it has become important to have anincreased degree of safety and modularity for any aircraft systemincorporating electronics or electric pumps, and it would beparticularly desirable to locate at least a portion of such systemsoutside of the cabin area of the aircraft. In any event, it is importantthat any system that interfaces with either food or the cabin area isnon-toxic and can be configured to provide a wide range of coolingcapacity as a function of the food and food carts that are to beinterfaced with such a system. The present invention satisfies these andnumerous other requirements for transport aircraft.

SUMMARY OF THE INVENTION

The present invention overcomes the shortcomings of previously knownsystems for cooling food carts in aircraft. The system of the inventionserves to not only remove the bulk of the refrigeration system from thegalley area but also obviates the need to accommodate bulky air ductsthat would supply cooled air from refrigeration stations directly to thecarts. Additionally, the system allows low temperatures to be readilyachieved in a very controllable manner.

In general terms, the invention employs an intermediate working fluid totransfer heat from a cart or carts to a remote chiller or chillers. In apresently preferred embodiment, the components of the system may beadvantageously positioned in the aircraft and do not have to becontained in a single location. More specifically, the inventionutilizes a plurality of heat exchangers to effect a cooling of the cartswherein heat from the food cart is first transferred to an airflow; heatfrom the airflow is then transferred to an intermediate working fluidwhich is circulated between a location immediately adjacent the foodcarts and a remote chiller; heat from the intermediate working fluid issubsequently transferred to the chiller working fluid; and finally, heatfrom the chiller working fluid is expelled to ambient air.

While in the currently preferred embodiment, the chiller working fluidundergoes a phase change in order to transfer heat from the intermediateworking fluid to the ambient air, the intermediate working fluidtypically remains in its liquid phase throughout its circulation. Arecirculation pump serves to circulate the intermediate working fluidthrough a distribution system that may link a plurality of chillers to aplurality of food carts. An expansion tank accommodates the expansionand contraction that the intermediate working fluid undergoes during itscirculation. Each of the chillers cycles the associated chiller workingfluid between a condenser and evaporator in a conventional mannerwhereby an expansion valve is relied upon to control the phase changetherebetween.

The temperature of the food cart is regulated by a combination ofcontrols. The speed of a fan circulating air flowing over the heatexchanger for the intermediate working fluid and directing the aircooled in this manner through the food cart may be varied so as toinfluence the rate of heat transfer between the food cart and theintermediate working fluid. A variable flow valve may be used to controlthe flow of intermediate working fluid to each cart, while the flowvelocity of the intermediate working fluid circulating in the entiredistribution system may be controlled by varying the speed of therecirculation pump. Finally, each of the chillers may be turned on oroff depending upon the temperature of the intermediate working fluidreturning from the food carts. Temperature sensors and pressure sensorsare positioned throughout the system to monitor these parameters atappropriate locations in order to allow the operation of the overallsystem to be properly controlled by the use of electronic controls suchas programmable industrial controllers. (PIDs)

Other features and advantages of the present invention will become moreapparent from the following detailed description of the preferredembodiments in conjunction with the accompanying drawings, whichillustrate, by way of example, the operation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a general overview of thegalley refrigeration system for aircraft according to the invention.

FIG. 2 is a schematic diagram illustrating the general design parametersof the galley refrigeration system for aircraft according to theinvention.

FIG. 3 is a schematic diagram of a distributed version of the galleyrefrigeration system for aircraft according to the invention.

FIG. 4 is a schematic diagram of a first version of a layout of adistributed galley refrigeration system for aircraft according to theinvention.

FIG. 5 is a schematic diagram of a second version of a layout of adistributed galley refrigeration system for aircraft according to theinvention.

FIG. 6 is a schematic diagram of a third version of a layout of adistributed galley refrigeration system for aircraft according to theinvention.

FIG. 7 is a schematic diagram of a fourth version of a layout of adistributed galley refrigeration system for aircraft according to theinvention.

FIGS. 8A and 8B are a schematic diagram of an electronic control systemfor controlling the galley refrigeration system for aircraft accordingto the invention.

FIG. 9 is a schematic diagram of a galley air cooling unit of the galleyrefrigeration system for aircraft according to the invention.

FIG. 10 is a signal block diagram of an electronic control system forcontrolling the galley refrigeration system for aircraft according tothe invention.

FIG. 11 is a diagram of a control panel for operation of the controlsystem for controlling the galley refrigeration system for aircraftaccording to the invention.

FIG. 12 is an overall thermodynamic chart of the galley refrigerationsystem for aircraft according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a system for refrigerating foodcarts within an aircraft galley system. Generally, the system includes aset of remote chillers which remove heat from a distributed liquidrefrigerant system, which in turn removes heat from one or more foodcarts to refrigerate the food carts. The entire system is electronicallymonitored and controlled to provide a sufficiently chilled environmentwithin a potentially large number of food carts.

More specifically, the present invention includes three distributedrefrigeration subsystems, and an electronic control subsystem formonitoring and controlling the refrigeration subsystems. The firstrefrigeration subsystem includes at least one remote chiller, the secondrefrigeration subsystem includes at least one galley air cooling unit,and the third refrigeration subsystem includes at least onerecirculation unit.

Each remote chiller constitutes a self-contained refrigeration unit,which serves to remove heat from a liquid refrigerant, referred to asthe intermediate working fluid. The intermediate working fluid is thendistributed to the second refrigeration subsystem. The galley aircooling units each include a galley cart and a galley plenum. Thechilled intermediate working fluid is distributed into and exits from aheat exchanger within the galley plenum. A blower or fan within theplenum blows air over the exchanger and through the galley cart. In thismanner, the galley cart may be continually flushed with air chilled bythe galley plenum heat exchanger.

Upon exiting the galley plenum the intermediate working fluid isdistributed to the third refrigeration subsystem. Each recirculationunit may include one or more liquid pumps and expansion tank oraccumulator. The one or more pumps of the recirculation units pressurizethe intermediate working fluid for redistribution to the remotechillers. The accumulators of the recirculation units allow for thestorage and thermal expansion of the intermediate working fluid.

The electronic control subsystem is also a distributed system which maymonitor and control individual components of each refrigerationsubsystem. Individual electronic devices may be used to monitor andcontrol the temperature within each galley cart. The galley air coolingunits may include a control valve to vary the amount of liquidrefrigerant entering the galley plenum. The electronic devicesmonitoring the temperature of the air in the galley cart may be used toadjust the control valve. These same electronic devices may also be usedto turn the fan in the galley plenum on and off.

Other electronic devices may be used to monitor and control therecirculation units. These electronic devices monitor and control therecirculation units. These electronic devices may also be configured tomonitor the pressure and volume within the expansion tank. Therecirculation units may be controlled by turning the pumps on and off orby varying the speeds by which the pumps operate.

Other electronic devices may also be used to monitor and control theremote chillers. By monitoring the pressure and temperature within theremote chiller the electronic devices can appropriately determine whichremote chillers to operate at different times.

The electronic subsystem may be powered by the aircraft electrical powersystems. The electronic subsystem may also include any number of displaysystems and interfaces for control by the crew. An overall controlsystem may operate each individual electronic device.

The entire system and each individual component should be configured foroperation within the unique environment presented by transport aircraft.Equipment used on commercial aircraft must meet strict requirements. Inaddition to maintaining food at safe temperatures, general aircraftoperating requirements must be met. The size and weight of the systemmust be kept to a minimum. The reliability and ease of maintenance arekey economic considerations. Fire suppression, non-toxicity andelectromagnetic interference (EMI) shielding are key safetyconsiderations. The present invention allows for these concerns, andothers, to be met satisfactorily.

As depicted in FIG. 1, several components combine to form a galley aircooling unit 18. A galley cart 20 is typically stored within a galleyplenum 22 while storing food. To safely store the food the air withinthe galley cart must be stored at or below a specific temperature. Forexample, 39° F. (4° C.) is the temperature required by certain agencies.The galley plenum is equipped with gaskets to form an air tight sealwith the galley cart. Preferably the galley plenum is equipped with ablower 24 or fan which circulates air throughout the galley cart andover at least one heat exchanger 26 within the galley plenum. Ducts 25between the galley cart and the galley plenum direct the flow of airacross the stored food.

The heat exchanger 26 within the galley plenum 22 may include a plateand fin configuration optimized for removing heat from passing air. Thepresent invention contemplates the exchange of thermal energy betweenambient air and a liquid refrigerant, also referred to as a heattransfer fluid, or the intermediate working fluid 27. A known heattransfer fluid having appropriate thermal and physical properties foruse with the present invention is a fluorinated heat transfer fluid soldunder the trademark GALDEN® HT 135. GALDEN® HT 135 is aperfluoropolyether or PFPE fluid sold by the Ausimont Montedison Group,although other similar heat transfer fluids may also be suitable.

A large number of the galley carts 20 (e.g., 45) may be required on asingle aircraft. In a currently preferred embodiment, each galley cartmay require a thermal exchange of approximately 750-1000 BTUs per hour.The corresponding air flow requirement of each galley cart in such anarrangement would then be approximately 72 cubic feet per minute. Thecorresponding fluid flow through each heat exchanger 26 would beapproximately 0.64 gallons per minute (using GALDEN®HT 135). Systems inaccordance with the present invention may be designed to meet theserequirements for as many galley carts as are used on an aircraft.

A proportional flow valve 28 may be used to control the flow of theintermediate working fluid 27 from each heat exchanger 26 within thegalley plenum 22. It is also contemplated that a single proportionalflow valve may control the flow of fluid into two or more heatexchangers. One method of controlling the temperature of the air withinthe galley cart 20 is to electronically manipulate the proportional flowvalve so as to regulate the flow of fluid into the heat exchanger.

As depicted in FIG. 1, the source of the chilled intermediate workingfluid is at least one remote chiller unit 30. After exiting the heatexchanger 26 within the galley plenum 22 the intermediate working fluidis no longer chilled. The unchilled intermediate working fluid isreturned to the chiller unit via the valve 28, cooled, and redistributedthroughout the system by at least one recirculation unit 32.

As depicted schematically in FIG. 2, a simple system conforming to thepresent invention may consist of a remote chiller unit 30 and aredistribution unit 32 refrigerating several galley carts 20. As anexample, the liquid chiller unit may be configured as a vapor cyclerefrigeration unit. In such a unit, a compressor 34 (a pump or othermachine that increases the pressure of a gas) may be powered by theaircraft's electrical system. Preferably, a rotary-type compressor isused to compress low temperature and pressure vapor into hightemperature and pressure super-heated vapor. The material to form thisvapor is also a refrigerant and may be referred to as a chiller workingfluid 35 (See FIG. 1). A known material which has appropriate thermaland physical properties for use with the present inventions as thechiller working fluid is a hydrofluorocarbon refrigerant such as thatsold under the name HFC-134a available from DuPont, or sold under thename MEFOREX 134a, or HT 134a, available from Ausimont, as a replacementfor CFC12, although other similar refrigerants may also be suitable.

From the compressor 34, the chiller working fluid 35 flows into acondenser 36. The condenser is preferably configured as a tube-fin heatexchanger to maximize heat rejection. From the condenser, the chillerworking fluid flows through an expansion valve 38 into an evaporator 40.The evaporator is preferably configured as a plate-fin heat exchanger tomaximize heat absorption.

Associated with the evaporator 40 is an expelling heat exchanger 42. Theintermediate working fluid 27 flows through the expelling heatexchanger. The association of the evaporator with the expelling heatexchanger forms a chiller unit heat exchanger 43 (see FIG. 1) andenables a thermal exchange between the intermediate working fluid andthe chiller working fluid 35 without the fluids ever mixing. As thechiller working fluid passes through the evaporator 40, back into thecompressor 34, it draws heat from the expelling heat exchanger and theintermediate working fluid.

A remote chiller unit 30 in accordance with this invention may berequired to maintain a required low temperature in several galley carts20. As an example, the total heat rejection required of a single remotechiller unit may be 18,000 BTUs per hour. This would require a flow rateof the intermediate working fluid 27 of 4.6 gallons per minute (usingGALDEN® HT135). A corresponding flow rate through the condenser would be700 cubic feet per minute at 3.5 inches H₂O pressure (using HT-134a).This could be supplied by a condenser blower wheel operating at 5,750revolutions per minute. Further requirements of such a remote chillerunit 30 may be an air venting fan as well as a mechanical bypass valve.

The unchilled intermediate working fluid 27 flows out of the heatexchanger 26 in the galley plenum 22 and is redistributed to a liquidpump 44 in at least one recirculation unit 32. The liquid pump may beconfigured as a turbine impeller pump which delivers relatively highpressure at relatively low flow rates. The liquid pump should beentirely sealed to prevent any leakage of the intermediate workingfluid. The liquid pumps supply all the force required to maintain thecirculation of the intermediate working fluid through the components ofthe system.

Within the recirculation unit 32, the intermediate working fluid 27flows into an expansion tank 46. The expansion tank functions as anaccumulator and a reservoir for the intermediate working fluid. Theexpansion tank allows for thermal expansion of the intermediate workingfluid. Preferably, throughout the entire process, the intermediateworking fluid remains in the liquid state.

Each recirculation unit 32 may gather intermediate working fluid 27 fromseveral galley air cooling units 18. Each recirculation unit may alsoprovide intermediate working fluid to several remote chiller units 30.As an example, the flow rate through a single recirculation unit may be10 gallons per minute. The recirculation units may also be required toprovide a pressure differential of 100 pounds per square inch in theintermediate working fluid.

As depicted in FIG. 3, systems conforming to the present invention maybe distributed systems. That is, a plurality of remote chiller units 30may combine to remove heat from a plurality of galley carts 20, and theentire system may be continually recirculated by at least onerecirculation unit 32. This permits the remote chiller units 30 andrecirculation units 32 to be located at an accommodating distance fromthe galley carts 20. Because of the limited space available oncommercial transport aircraft this can be very advantageous.

To circulate the intermediate working fluid 27 throughout thedistributed system, a network of ducts connects the individualcomponents. Supply ducts 48 are configured to distribute the chilledintermediate working fluid to the galley air cooling units 18.Redistribution ducts 49 are configured to route the unchilledintermediate working fluid to the liquid pumps 44. Return ducts 50 areconfigured to distribute the unchilled intermediate working fluid to theremote chiller units 30.

FIGS. 4-7 depict various configurations of the present invention. Thediffering configurations of various commercial aircraft require a greatdeal of flexibility in placement of remote chiller units 30 andrecirculation units 32. As the galley carts 20 may be distributed invarious galleys throughout the aircraft, the supply ducts 48,redistribution ducts 49 and return ducts 50 may run potentiallythroughout the entire aircraft. The present invention allows each of thecomponents of the refrigeration system to be distributed toaccommodating locations within the galleys or nearby.

As depicted in FIGS. 8A and 8B, the present invention may also include acomprehensive electronic subsystem to monitor and control thedistributed refrigeration system. A galley cart control device 52 may beassociated with each galley air cooling unit 18. An air outlettemperature sensor 54 and an air supply temperature sensor 56 may eachprovide input to the galley cart control device. The galley cart controldevice may then turn on or off the blower 24 as well as control theoutput of the proportional flow valve 28.

A chiller unit monitoring device 58 may be associated with each remotechiller unit 30. By means of a pressure transducer 60, a thermo-sensor62 and a current sensor 64 the chiller unit monitoring device maymeasure the function of the remote chiller unit. If needed, the chillerunit monitoring device could shut down the remote chiller unit.

A system monitoring and control device 66 may be associated with eachrecirculation unit 32, or may be associated with the system as a whole.The system monitoring and control device may monitor the volume andpressure within each expansion tank 46 as well as the functioning of theliquid pumps 44. Furthermore, the system monitoring device may monitorthe temperature and pressure of the intermediate working fluid 27 atvarious locations within the system. The system monitoring and controldevice may also receive input from the chiller unit monitoring devices58 and the galley cart control devices 52. With this information, thesystem monitoring and control device may control the functioning of eachand every electronic and refrigeration component of the entire system.

As depicted in FIG. 9, the galley cart control device 52, may controlthe temperature of the air in the galley cart 20 by regulating the flowof the intermediate working fluid 27 into the heat exchanger 26 withinthe galley plenum 22. The air supply temperature sensor 56 measures thetemperature of the cold supply air and relays that information to thegalley cart control device. In order to ensure that the cold supply airremains near a specified temperature (e.g. 30° F. (−1° C.)) the galleycart control device can increase or decrease the flow of intermediateworking fluid by controlling the proportional control valve 28. As theflow of the intermediate working fluid into the heat exchanger increasesthe temperature of the supply air will decrease and vice versa. Thegalley control device may also monitor the temperature of theintermediate working fluid at various locations or the temperature ofthe air returning to the heat exchanger. Furthermore, a differentialpressure gauge 59 on the supply ducts 48 and a flow meter 61 on theredistribution ducts 49 may provide additional information about theflow of intermediate working fluid into and out of the galley aircooling unit 18. The galley cart control device could use this furtherinformation to more efficiently regulate the proportional flow valve orto turn the blower 24 on and off.

As depicted in FIG. 10 the components of the electronic subsystem may beinterrelated via the system monitoring and control device 66 alsoreferred to as the recirculation unit with control logic. That is, thesame electronic device used to monitor and control the recirculationunit 32 may be programmed to control the overall functioning of theentire system. This may include such functions as malfunction detectionand providing maintenance information. Each galley cart control device52 and chiller unit monitoring device 58 may be configured to sendsignals to the system monitoring and control device relaying informationabout the status of the galley air cooling units 18 and remote chillerunits 30. In turn, the system monitoring and control device could sendsignals back to the galley cart control device and chiller unitmonitoring device instructing the devices on how to control each galleyair cooling unit and remote chiller unit.

As depicted in FIG. 11, at least one display 70 may be included with theelectronic subsystem. The display enables crew interface with therefrigeration system. A set of lights indicates the status of thevarious components. A set of switches may permit crew control of thevarious components. The display may be electronically controlled by thesystem monitoring and control device 66.

FIG. 12 depicts a thermodynamic chart showing the functioning of therefrigeration subsystems. The information provided by the chart isexemplary of a system in accordance with the present invention. Thechart depicts the refrigeration process as a series of heat exchangesbetween the various fluids involved in the process.

It will be apparent to those of skill in the art that the exemplarysystems described in this detailed description conform to the inventiondescribed. It will also be apparent to those of skill in the art thatvarious modifications may be made to the exemplary systems whileremaining within the scope of the invention. Thus, the invention is notintended to be limited to the examples described herein. The scope ofthe invention is described and limited only by the following claims.

The invention claimed is:
 1. A system for cooling of onboard food cartson aircraft, comprising: a first working fluid loop configured tocirculate a first working fluid, said first working fluid loop includinga galley plenum including a galley plenum heat exchanger fortransferring heat from the galley plenum to said first working fluid, avalve configured to control the flow of said first working fluid throughsaid galley plenum heat exchanger, a first working fluid pump configuredto pump said first working fluid to said galley plenum heat exchanger,said first working fluid pump being located remotely from said galleyplenum heat exchanger, an expelling heat exchanger, said first workingfluid pump being configured to pump said first working fluid throughsaid expelling heat exchanger, and a blower for blowing air through saidgalley plenum heat exchanger and said galley plenum; a second workingfluid loop circulating a second working fluid through a condensor andthrough an evaporator associated with said expelling heat exchanger ofsaid first working fluid loop, said second working fluid loop includinga second working fluid pump connected between said evaporator and saidcondensor, and an expansion valve connected between said condensor andsaid evaporator, said second working fluid pump being configured to pumpsaid second working fluid through said condensor to cool said secondworking fluid and through said evaporator to cool said first workingfluid in said expelling heat exchanger of said first working fluid loop;and a display configured to indicate a status of said first workingfluid pump, said valve and said blower, said display including aninterface for controlling said first working fluid pump, said valve, andsaid blower in order to control the temperature within said galleyplenum.
 2. The system of claim 1, wherein said expelling heat exchangerand said evaporator are located remotely from said galley plenum.
 3. Thesystem of claim 1, further comprising an expansion tank connected influid communication with said first working fluid pump for receivingsaid first working fluid for accommodating any expansion or contractionof said first working fluid, said expansion tank being located remotelywith respect to said galley plenum.
 4. The system of claim 1, whereinsaid first working fluid undergoes no phase change at any time.
 5. Thesystem of claim 4, wherein said first working fluid remains in a liquidphase at all times.